Mainstream's prior research has already demonstrated a highly-sensitive real-time carbon nanotube (CNT) sensor for the detection of water-borne arsenic and a determination of the arsenic concentration. This Phase I concentrates on extending and improving the earlier work by investigating the effects of the following on CNT CVD growth: substrate substance, patterning of the oxide or metal catalyst, catalyst deposition technique, CVD method, and CVD parameters. How these factors affect sensor discharge voltage and uniformity will be analyzed using a complete Design of Experiment (DOE) and standard Analysis of Variance (ANOVA) methodology. The end goal is to make CNT mats that are more uniformly perpendicular to the substrate which will result in a lower operating voltage and more uniform functionality between different devices. Phase II will concentrate on the design of all extraneous subsystems (scrubber, arsenic to arsine conversion, electronic display, etc.) and the physical and thermal packaging of the complete sensor. [unreadable] [unreadable]